Bionic Brains and Memory: World's First Brain Prosthesis?

Is your memory failing? Considered popping in a memory chip? This week,philosophical fantasies meet the world of the modern 'neural engineer'. All In the Mind ponders a curious future where brains are wired to computers, and silicon neurons replace your own. Scientists have just developed an early silicon model for an artificial hippocampus, a part of the brain so crucial to our sense of self. Its helps us make memories, and is often damaged in those with Alzheimers or after a stroke. But will these silicon recollections be your own?

Transcript

Natasha Mitchell:Hello, Natasha Mitchell here with you for All in the Mind and today, getting inside your head to look at the prospect of a bionic brain.

Carl Craver: We might have thought prior to the development of artificial hearts that having taken someone's heart out and replaced it with a piece of plastic and metal would have stolen their soul in some way, taken something that was very particular to them.

We're used to thinking of prosthetics as replacements for the tools with which we carry out our will. So we think of prosthetics as replacements for arms, or replacements for eyes, or replacements for ears. But we're not used to thinking of replacements for the very things that would have desire, the very things that would make decisions about our futures, the very things that shape our conception of who we are and so shape how we will act in the future.

Natasha Mitchell:Philosopher Carl Carver considering prosthetic replacements for when things go wrong inside your head. This month researchers in the vanguard of neuroscience gathered for the first International Conference on neural engineering in Italy.

What caught the attention of the world's journalists was a presentation given by a leading biomedical engineer who hopes to wire up human brains with a silicon interface, even in the next decade or so.

"World's first brain prosthesis" screamed the headlines. Theodore Berger and his team at the University of Southern California report that they've developed a prototype artificial hippocampus. That's the part of the brain involved in the storage of information as memories, and so crucial then to who we are. Conditions like Alzheimers, epilepsy or a stroke can damage the hippocampus and more on that later.

But the research team's ultimate goal is:-

"To develop a neural prosthetic for the central nervous system to replace higher thought processes that have been lost due to damage. A neural prosthetic designed to replace damaged neurons in central regions of the brain with silicon neurons."

The scientists aren't accepting invitations to talk about it but let's be clear what we have here. A microchip, that was modelled by passing many electrical impulses through rat hippocampus cells and measuring the outputs. The device is about to be trialed in the test tube in slices of rat tissue to see if it will connect up with real neurons and work like part of a hippocampus should. It's a long way from humans yet, where the vision is that such as chip could sit outside of the skull.

But this sort of work raises some especially juicy ethical and philosophical questions. Like - does this point to the possibility of bionic memory for all of us - and would the memories mediated by an artificial hippocampus be a person's own?

Carl Craver is a philosopher of neuroscience at Washington University in St. Louis, and one that likes to keep brain scientists on their toes.

Carl Craver: Memory is at the heart of our personality and the prospect of replacing the hippocampus with an electrical implant moves from 'prothesis as tool' to 'prothesis as decision maker'. And that raises a whole host of questions that I don't think that we've adequately grappled with yet.

Natasha Mitchell:Yes, the bio-ethicist Arthur Caplan, who's fairly optimistic about the brain revolution, he suggests that we're a little puritanical about the idea of mucking with our heads. And this taps into this concern that you've expressed.

Carl Craver: Right. One thing that I should do to temper my concern about this is to simply point out that we tend to think of cognition as something that happens inside our skulls, or at least inside our skins. But it's important to keep in mind that a lot of what we would call cognitive activity involves tools in our environment. We already count on our fingers and do math on paper, and we remember things by writing them down in our day planners, we drive to a new city by following the road signs along the way and all of those things are ways of using our environment as what Andy Clarke calls "scaffolding for thinking".

And so there's a real question about what difference there is between those kinds of environmental "scaffolding" and the kind of scaffolding that Burger's advance forces us to think about. What difference does it make whether the information that we're using in our environment is used by us through visual signals or auditory signals, or whether they're used through electrical signals running down wires.

Natasha Mitchell:So this notion of the "extended mind" that some philosophers are keen to propagate that the mind is not encapsulated in our brain, not even within our body, but it is also so much integrated into our environment, our interactions.

Carl Craver: That's exactly right and that raises the question what's the difference between these normal cases of extended cognition that we use unthinkingly on a daily basis, and the kind of unextended cognition that we're confronted with in the case of Burger's putative discovery.

Natasha Mitchell:But before we get too philosophical about the prospects of a brain prosthesis let's just be reminded of what it's thought the hippocampus we're born with does.

Like most bits of the brain we usually find out what they do when something goes wrong with them. And as neuropsychologist Dr Jonathan Foster knows all too well, life can go radically astray without a healthy hippocampus.

He heads up a Memory and Brain Lab at the University of Western Australia.

Jonathan Foster: The hippocampus seems to be particularly involved in creating new long term memories. So if I can give you a concrete example, we've been studying a gentleman in Perth in Western Australia who's had selective hippocampus injury and that means that in a sense he's living in a time warp because he's finding it very difficult, if not impossible. to create new, long term memories.

So for instance one of the things he reports to me is that he's quite a wine connoisseur and he finds it quite difficult now to go into the local wine store and select a good bottle of wine because he can't update his knowledge. In fact his memories for wine stops in about 1998, 1999 when the injury occurred to his brain.

Natasha Mitchell:That might have been a good year, for a good vintage drop...!

Jonathan Foster: Yes, but the problem he's finding is that more and more of those wines are disappearing from the shelves you know, and the more recent wines he can't learn any new information, he can't put any of that information into long term storage. If you like he can't put it onto the 'hard drive' so it's there when he wants to go back and retrieve it.

Natasha Mitchell:And hard drive of course is the outer layer of our brain, the cortex so memories are sort of processed by the hippocampus, I take it, and then they're stored for the long term in some sense in the cortex.

Jonathan Foster: Yes, well the traditional view that's emerged over the last few decades is that the hippocampus functions more as the printing press not as the library, so it's not the ultimate repository for these long term memories that we create to give ourselves an enduring and ongoing and updated sense of self. The hippocampus isn't storing these memories indefinitely. But over time the conventional wisdom has been that those memories become 'downloaded', if you like, into the cortex, into the outer bark-like covering of the brain which has become so expanded in humans relative to other species.

Natasha Mitchell:Jonathan Foster.

But to help you better visualise where exactly the hippocampus sits in the mass of porridge that we call our brain, Carl Craver.

Carl Craver: Yeah, the hippocampus is a brain region in what's known as the temporal lobes. If you look at a picture of the brain from the side the temporal lobes would be that large fleshy piece that comes across the bottom of the brain. And if you were to turn the brain upside down and look at its bottom you could see just a hint of the hippocampus heading up in a circular fashion into the centre of the brain.

And this is a primitive organ, it has a very regular cellular structure that's repeated all along its length, and so one of the ways that researchers have been studying the hippocampus is by slicing it, into paper-thin slices that preserve the cellular organisation of that structure. And they can do electro-physiological experiments of stimulating cells and recording from other cells all along that structure by simply taking slices out and studying them in isolation.

So the hippocampus originally attracted attention in the 1950's because of its association with epilepsy. And then in the late 1950's, mid 1950's, as a result of extremely life threatening epilepsy a patient who is now knows as 'HM' agreed to an experimental surgical procedure to remove the hippocampus. And when he awoke he was fine for all intents and purposes, his sensory motor skills seemed to be together, his language was just fine, his IQ, if anything, increased as a result of the surgery although not statistically significantly.

Natasha Mitchell:But something terrible happened to him didn't it?

Carl Craver: Yeah, something quite terrible. Then when he had lost the ability to lay down new declarative memories, new memories for facts and events and this suggested to a number of researchers that the hippocampus played a crucial role in the encoding of memory in the brain. So that's 'Hippocampus 101'.

Natasha Mitchell:Well this month the heady headlines in New Scientist, Jonathan Foster, were "world's first brain prosthesis" and it was actually pointing to a silicon hippocampus. When you read headlines like this, are you spooked?

Jonathan Foster: Well in theory that is feasible with sufficient levels of knowledge in terms of the potential for electric conduction between carbon based if you like biological tissue and silicon based tissue such as a chip. The problem lies in actually characterising what the hippocampus actually does and we're still struggling to determine precisely how the hippocampus works in laying down these new long term memories.

So for instance we don't really know properly why of all the rich tapestry of experience that we're subjected to on a daily basis, certain elements of that experience are laid down as memories and other elements of that experience are not. They're discarded. Now we think it could be something to do with our evolutionary past and if situations occur which could be potentially threatening, or potentially rewarding then certain signals are triggered which indicate that this should be stored information, this information should go into the hippocampus and be processed by the hippocampus. But that's still a mystery to some degree.

Natasha Mitchell:Yes the other argument might me that even if we don't really totally understand the full operational function of the hippocampus the idea is that the brain is an adaptive organ so if you slot a chip in that almost does what the hippocampus does in terms of the electrical inputs and outputs in the brain, then hopefully the brain will adapt around it, you know, it will take up some of the slack that the silicon equivalent can't actually achieve.

Jonathan Foster: There's a fundamental distinction here, Natasha, between seeking to try to understand the system - and with a system as complex as the brain which has been sometimes termed the most complex system in the known universe - where it becomes problematic is if we actually offer to patients such as the gentleman we have been studying in Perth some kind of false hope that we could actually substitute for the functional impairment that they have as a consequence of their brain injury, by slotting something into their brain which is currently only fairly crudely defined in terms of its functionality.

So, I don't think we can start opening up people's skulls and conducting neurosurgery and hoping that the brain will take up the slack if we're going to do it in an applied context. I think our knowledge as the authors acknowledge, of this paper, has to go beyond in-vitro models in the rats to in-vivo models.

Natasha Mitchell:In-vivo models being inserting a test chip actually into the living animal?

Jonathan Foster: That's correct and it's debatable whether the rat itself would be an adequate analogue for humans here because of the role of language and the richness of language and its significance in the mediation of human memory which obviously doesn't apply to any other species.

Natasha Mitchell:It seems impossible to think that all that could be achieved through a silicon chip.

Jonathan Foster: Well I think in principle, given, I mean I'm not an electronic engineer, but given that the appropriate level of detail could be etched into a chip and we may be getting then into the realm of quantum physics, I don't know, given the scale of these things. In principle it could be achieved. But I would say, as I've mentioned before, if we're going to start offering this as a ray of hope for people with Alzheimer's, people with epilepsy then we really need to be on firmer scientific ground, not only in terms of our technological prowess with bits of silicon, but also in terms of our fundamental neuroscientific understanding of what the hippocampus is doing, why it's doing it and what conditions it's subserving those functions.

Natasha Mitchell: Neuro-psychologist Dr Jonathan Foster from the University of Western Australia. And you're tuned to All in the Mind with me Natasha Mitchell coming to you on ABC Radio National and internationally on Radio Australia and the web.

Well the prospect of a silicon hippocampus is but the tip of an iceberg, there's a bigger story here about the convergence of engineering and neuroscience. If you think of the brain as little more than an electronic circuit of firing neurons, it's not unlike a computer after all. Or is it?

Carl Craver from Washington University joins philosophers throughout the ages with his interest in these sorts of tricky questions from neuroscience.

Carl Craver: The relationship between the mind and the body is a tradition philosophical question extending back to ancient Greece. So I maintain that sort of fascination. There are just questions about how for instance the taste of chocolate or the feeling of love, or the memory of a first kiss could be the kind of thing that could be explained in terms of the interaction among a number of distinct neurons. The second (reason) however, is a conviction that somebody needs to be looking at neuroscience from the outside and asking questions like, what kind of evidence would it take to show that that was right, and what reason do we have to believe that?

When I got into the philosophy of neuroscience this was in the late 1980's and it was then much more common that it is now to hear people talking about, for instance, 'male brains' and 'female brains', or 'male sides to the brain' or 'female sides to the brain', or 'gay' and 'straight brains'. And it struck me at that time that this looked very much like some of the phrenology and craniometry that was being done in the 19th Century. And it seemed to me that somebody needed to be there to look at this work and to ask the question, 'do we really have a solid evidential foundation for believing these claims', or 'should we be looking a bit more carefully?'

Natasha Mitchell:Well it seems to me that neuroscience is heading in directions that the early founders could never have imagined and that is attempts to bond brain and computer. This has been the fantasy of science fiction writers for years. But you've spent some time considering the history of neuroscience, how do you view efforts today to try and bond brain with computer through you know the fledgling development of silicon prosthetic devices to help perhaps repair or compensate for bits of the brain that are damaged?

Carl Craver: Well let's leave the prosthetic issue to one side for a moment and simply focus on the computational metaphor that's so ubiquitous in contemporary neuroscience.

If you take a look at the history of neuroscience, where should be begin - if you look at Descartes for instance, Descartes hopes to understand the entire operation of the nervous system in terms of contact action. That is simply in terms of extended particles and their collisions with one another. If you move slightly forward in time you find David Hartley who called himself the 'Newton of the Mind', trying to understand the behaviour of distinct neurons in terms of oscillations or vibrations moving along those neurons. And there he was making use of a Newtonian concept in an effort to understand the operation of the brain.

In Descartes you can also find accounts in terms of hydraulic fluids being shunted in one direction or another through the nerves.

And so at different times and different places you find people using different mechanical metaphors to understand the operation of the brain and in our day and age it's not surprising that we would reach to the most fascinating of machines in our environment, namely the computer.

Natasha Mitchell:So that's thinking of the brain as something like a computer with inputs and outputs and a black box in between. What about this concept that we might actually one day be able to fuse our brains with bits of silicon?

Carl Craver: That seems to me to be a very distinct possibility...

Natasha Mitchell:...The Cyborgian desire....

Carl Craver: Yeah, it seems to me that there's not in principle reason to think that that's not going to happen. In fact there's every good reason to think that it already has happened.

For example, one popular issue has to do with Cochlear implants in which people have been able to replace the hair cells in the ear that are responsible for transducing soundwaves into electrical signals in neurons, and those have been replaced by mechanical implants.

There are also cases of people using stimulation of the vagus nerve, this is more experimental, but stimulation of the vagus nerve in order to prevent the onset of epileptic seizures. Or there might be functional electrical stimulation to help solve problems of paralysis. I see those as very likely outgrowths in the short term future of research in the neurosciences. So, this isn't some distant future, this is something that to some extent is already here.

Natasha Mitchell:So when we hear news then, that researchers are spending a considerable amount of time and energy and have come up with what is an artificial hippocampus are we talking about the prospects of a memory chip here, or bionic memory?

Carl Carver: Before we discuss the implications of science fiction, it's important that we put the brakes on our interpretation of what's coming out of this laboratory.

In the first place it was announced as merely a test of such a chip not the discovery of such a chip. And in fact the only thing that's announced is that it's going to be tested on an in-vitro slice, the kind of slice that I was talking about earlier that researchers extract from the hippocampus and do their experiments on. And so it's a long way from being able to mimic the behaviour of a hippocampal slice, to being able to mimic the behaviour of the hippocampus in a rat or a rabbit. And probably a long way from being able to mimic the behaviour of the hippocampus in a rat and a rabbit to doing it in a chimpanzee, and from doing it in a chimpanzee to doing it in humans. And in addition, the report that I read about this suggested that they had a hippocampal chip that would work on 50 to 100 neurons, and they had plans for one that would work on 10,000 neurons. But I think it's important to keep in mind that the hippocampus in human beings is composed of somewhere around ten billion cells, making somewhere around 1000 to 100,000 connections between them, and so it's a long way from 50 to 100 neurons to 10 billion neurons.

Natasha Mitchell:They are still in the sandpit...

Carl Carver: We're definitely still in the sand pit. I think that this is an exciting development in part because it gives us an opportunity to ask, "how would you know that your model of the hippocampus was right?" And one plausible answer seems to be if it could serve the function of a real hippocampus then you would know that you in fact understood the way that it worked.

Natasha Mitchell:Let's talk about some of the ethical questions generally raised by the prospect of prosthetic devices that we can attach to our brains or embed in our brains, what people call 'neural prosthetics'. One of them might be for example if a person has damaged memory for example, because the hippocampus has been damaged, do they have the right sense of agency to decide whether they want a prosthetic device or not? Is their memory good enough to allow that to happen?

Carl Carver: It's very curious that you should ask that question. One thing, as I'm getting increasingly fascinated with memory and its relationship to the self, one thing that has struck me in reading the case reports of amnesic patients, is that researchers have not paid much attention to questions about the ability of these patients to make decisions for themselves and to act. As I said, people with bilateral, hippocampal oblation tend to be perfectly normal in many respects mentally but seem to lack simply the ability to track their own behaviour over time and to acquire new facts.

Now there are a whole range of questions - what happens if somebody who has this sort of memory disorder makes a promise at one time, should they be held to that promise at a later time? Or if they act in accordance with the promise does that count as actually keeping the promise or is that simply doing something that would be keeping the promise if they in fact remember having made the promise?

And there's a question about what to do in the case where somebody who in their brain damaged state refuses to take the prosthetic implant - although with the prosthetic implant they might agree to it entirely.

Natasha Mitchell:I mean, I'm fascinated by that question that you raised just then about when someone with a prosthetic device embedded in them, especially in their brain, does something - then whose accomplishment is it?

Carl Craver: Yeah, there's a real question about apportioning praise and blame - although I was reminded that this is not unique to the hippocampal case, just today when I was late for an appointment because I had misrecorded it in my day planner. Do you blame me or do you blame my day planner? Well in the case of somebody with a hippocampal replacement if they do something that is wildly out of character would it be a possible defence in court to simply say my "hippocampus made me do it?" "It's not my fault, it's the people who made the hippocampus, go blame them".

Natasha Mitchell:Associate Professor Carl Craver, historian and philosopher of neuroscience at Washington University in St Louis. And that's it for the show today and given that none of us actually have a bionic hippocampus in place just yet - a reminder that transcripts of all our programs are on the net.

Our email address is mind@your.abc.net.au - write to us, we want to hear from you. Thanks this week to sound engineer Steven Tilley, producer Sue Clark and I'm Natasha Mitchell - until next week, take care.

Guests

Carl F. Craver

Associate Professor (Historian and philosopher of neuroscience)'Philosophy, Neuroscience and Psychology' Program Department of Philosophy Washington University in St Louis USA